Merge branch 'doc-note-saml-as-requiring-pat' into 'master'

Document SAML as also requiring PATs

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/145898



Merged-by: Jon Glassman <jglassman@gitlab.com>
Co-authored-by: Katrin Leinweber <kleinweber@gitlab.com>